Madagascar’s history of colonisation

A huge mystery of human history may have been solved, thanks to ancient cooking scraps.

Alison Crowther from The University of Queensland, Australia, and colleagues from around the world dug up crop seeds from the 8th to 10 centuries on the African island of Madagascar and compared them to seeds from east Africa and surrounding islands. They found crop cultivars on Madagascar to be distinctly Southeast Asian and consistent with human migration.

The work was published in the Proceedings of the National Academy of Sciences.

The island of Madagascar is an incredible place, and not only because 90% of its wildlife is found nowhere else on Earth.

The Malagasy people speak Austronesian, a language otherwise only used by those in Southeast Asia and Pacific island nations more than 6,000 kilometres away – not an African language, despite being less than 500 kilometres from its east coast.

Yet archaeologists have failed to turn up evidence of an early Southeast Asian presence on the island in texts or in digs.

Some 10% of the island’s plant species are introduced, with many of Asian origin, such as rice, yam, taro and coconut. Could they have been brought to the island by ancient colonisers? If so, they would be the first evidence for a Southeast Asian presence between the 8th and 10th centuries.

Crowther and her colleagues collected sediments from 18 archaeological sites around Madagascar, coastal eastern African and nearby islands such as Zanzibar, and the Comoros archipelago, which is situated just north of Madagascar but closer to the African mainland.

They sifted burnt plant remains, picked out the seeds and examined them under a microscope to identify their species and origin. All in all, they found 2,443 plant remains which were radiocarbon dated to the correct era.

Seeds found on eastern African sites were mostly of African origin, with some Asian cultivars found around major ports such as Tanzania. This is consistent with commercial exchange activities, where foreign cultivars turn up in small quantities and are confined to port areas.

But on the Comoros and Madagascar, the seeds were overwhelmingly Asian. Rice was, by far, the most commonly found seed, comprising 70-100% of samples tested. The consistency of seed origin points to colonisation rather than trade.

Crops such as bananas and taro, which don’t leave seeds, weren’t included in the study – although they may be examined one day through microfossil analysis.

And while the work gives archaeological weight to Southeast Asian colonisation of Madagascar, the migration probably wasn’t straightforward. The presence of Asian grain on nearby islands suggest settlers may have first happened upon them first before making the journey to Madagascar.

It also raises questions about the Comoros. While the Comoros’ seeds were also from Southeast Asia, Comorians speak the African Bantu languages – not Austronesian.

Genetic analyses of Comorians find very little Southeast Asian ancestry. So what happened?

The researchers suggest the Comoros may have been first settled by Southeast Asian colonisers, but over hundreds of years of slave raiding and trading, and input from Bantu-speakers, it was “genetically and linguistically swamped”.